1. Field of the Invention
This invention relates to a compact reading apparatus for use for the reading of a facsimile apparatus or the like.
2. Description of the Prior Art
As one of the reading systems for a facsimile apparatus or the like, there is a system in which an original is intermittently moved in a secondary scanning direction, namely, in the direction of the shorter side of a slit, and a reading scanning head having a solid state image pick-up element such as CCD having the array direction thereof set in parallelism to the secondary scanning direction is reciprocated in a primary scanning direction, namely, in the lengthwise direction of the slit orthogonal to the secondary scanning direction, whereby an original image is read for each of a plurality of lines corresponding to the number of arrays of the solid state image pick-up element.
The illuminating system in such reading apparatus must effect, for example, illumination of 1/8 mm at GIII of CCITT standard and 1/6 mm at GII in the primary scanning direction and illumination of a length corresponding to the number of arrays of the solid state image pick-up element in the secondary scanning direction, namely, linear illumination elongated in the secondary scanning direction.
An apparatus disclosed in Japanese Laid-open Patent Application No. 74621/1979 is known as such reading apparatus, and this reading apparatus is shown in FIG. 1 of the accompanying drawings. In FIG. 1, reference numeral 1 designates an original which is intermittently fed in the direction of arrow 2 (secondary scanning direction). Reference characters 3a and 3b denote rod-like illuminating light sources which illuminate the slit width areas 6a-6b of the original 1, and an image element of the slit width areas 6a-6b is projected upon a solid state image pick-up element 5 arranged in the secondary scanning direction by an imaging lens 4.
The illuminating light sources 3a, 3b, the imaging lens 4 and the solid state image pick-up element 5 together constitute a reading head 7 which is reciprocated in the direction of arrow 8 (primary scanning direction). Thus, by one reciprocal movement of the reading head 7, reading-scanning of a plurality of lines is accomplished at the same time.
However, this apparatus has suffered from a problem that movement of the light sources 3a and 3b reduces the life thereof and unless the light sources are firmly fixed to the reading head, the positions of the light sources become deviated during movement of the reading head, thus resulting in irregular illumination.
To overcome such disadvantage, a reading apparatus in which the light source is fixed as shown in FIG. 2 of the accompanying drawings has heretofore been proposed. In FIG. 2, the original 1 is intermittently fed in the direction of arrow 2 (secondary scanning direction). Reference numeral 9 designates an illuminating light source such as a fluorescent lamp fixedly provided to effectively illuminate the entire lengthwise area of the slit, and reference numeral 10 denotes a fixed reflecting mirror for illuminating the entire area of the slit width areas 6a-6b of the original 1 in the primary scanning direction. An image element of the slit width areas 6a-6b of the original 1 in the primary scanning direction is projected upon a solid state image pick-up element 5 set in the secondary scanning direction, by an imaging lens 4. The imaging lens 4 and the solid state image pick-up element 5 together constitute a reading head 11 which is reciprocated in the direction of arrow 8 (primary scanning direction). However in the reading apparatus shown in FIGS. 1 and 2, the illuminating light source always illuminates the entire area of the slit width areas 6a-6b in the primary scanning direction and therefore, the light of the light source is not efficientl utilized and irregular illumination occurs in the array direction of the solid state image pick-up element.
Further, U.S. Pat. No. Re 29,017 discloses an optical system in which a point source of light is fixed an illuminating light beam is made into a substantially rectangular parralel light beam in a cross-section perpendicular to the optical axis and finally linear illumination is effected.
In this system, the light source is fixed to thereby prevent reduced life thereof, but in order to obtain an illuminating light source having a substantially rectangular cross-section, it has been necessary to use a mirror of complicated configuration called a parabolic mirror having a refractive power in two directions in a cross-section perpendicular to the optical axis.